When training for a marathon the two main aspects of your training will focus on building up the number of miles that you cover and introducing long runs into your regime to build up your endurance over distance. However, there are two other areas that you should also be working on and that is your speed and strength. You may consider this strange as a marathon is for running not raising dumbbells above your head. However they are very important and this is why:
1) Strength is essential for power and endurance. Without building strength into your body particularly your legs, arms and cardiovascular system you will blow out in the middle of a marathon even if you can reach that far.
2) In terms of speed this will enable you run at a faster pace during the race compared to your usual training speed. Speed in relation to long distance running is not to be compared to with sprinting. It is about speed work which is something different. This involves you running at a certain distance within certain time periods and having a rest or a recovery break in between. These types of training increases your fitness level over time it will not help you run the 100m under 10 seconds.
After a while many marathon runners will hit that infamous plateau. This means that no matter how many marathons you run your speed remains the same or even dips below your average. At his point you should incorporate more speed work sessions into your training regime in order to help improve your speed times.
If you are running a marathon for the first time then, it is too much for you to focus on speed and strength when there are so many other things to prepare for. For your first one it is best to focus on building up the number of miles that you run each week. You should aim to include a weekly long run into training schedule as this will prepare your body for the distance it has to run in a marathon. You can also do additional training to support the mileage and endurance targets with a mixture of drills and starting strides and circuit training. You can also mix things up a little by running shorter distances and then for the next training session run a longer distance. For most people who are entering their first marathon their main goal should be to complete it.